The Tor Browser: comparison mobile/android/base/favicons/decoders/ICODecoder.java

--1:000000000000
+:33bb2f21a81c
+/* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+package org.mozilla.gecko.favicons.decoders;
+import android.graphics.Bitmap;
+import org.mozilla.gecko.favicons.Favicons;
+import org.mozilla.gecko.gfx.BitmapUtils;
+import android.util.SparseArray;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+/**
+* Utility class for determining the region of a provided array which contains the largest bitmap,
+* assuming the provided array is a valid ICO and the bitmap desired is square, and for pruning
+* unwanted entries from ICO files, if desired.
+*
+* An ICO file is a container format that may hold up to 255 images in either BMP or PNG format.
+* A mixture of image types may not exist.
+*
+* The format consists of a header specifying the number, n,  of images, followed by the Icon Directory.
+*
+* The Icon Directory consists of n Icon Directory Entries, each 16 bytes in length, specifying, for
+* the corresponding image, the dimensions, colour information, payload size, and location in the file.
+*
+* All numerical fields follow a little-endian byte ordering.
+*
+* Header format:
+*
+*  0               1               2               3
+*  0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+* |  Reserved field. Must be zero |  Type (1 for ICO, 2 for CUR)  |
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+* |         Image count (n)       |
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+*
+* The type field is expected to always be 1. CUR format images should not be used for Favicons.
+*
+*
+* Icon Directory Entry format:
+*
+*  0               1               2               3
+*  0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+* |  Image width  | Image height  | Palette size  | Reserved (0)  |
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+* |       Colour plane count      |         Bits per pixel        |
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+* |                   Size of image data, in bytes                |
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+* |      Start of image data, as an offset from start of file     |
+* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+*
+* Image dimensions of zero are to be interpreted as image dimensions of 256.
+*
+* The palette size field records the number of colours in the stored BMP, if a palette is used. Zero
+* if the payload is a PNG or no palette is in use.
+*
+* The number of colour planes is, usually, 0 (Not in use) or 1. Values greater than 1 are to be
+* interpreted not as a colour plane count, but as a multiplying factor on the bits per pixel field.
+* (Apparently 65535 was not deemed a sufficiently large maximum value of bits per pixel.)
+*
+*
+* The Icon Directory consists of n-many Icon Directory Entries in sequence, with no gaps.
+*
+* This class is not thread safe.
+*/
+public class ICODecoder implements Iterable<Bitmap> {
+// The number of bytes that compacting will save for us to bother doing it.
+public static final int COMPACT_THRESHOLD = 4000;
+// Some geometry of an ICO file.
+public static final int ICO_HEADER_LENGTH_BYTES = 6;
+public static final int ICO_ICONDIRENTRY_LENGTH_BYTES = 16;
+// The buffer containing bytes to attempt to decode.
+private byte[] decodand;
+// The region of the decodand to decode.
+private int offset;
+private int len;
+private IconDirectoryEntry[] iconDirectory;
+private boolean isValid;
+private boolean hasDecoded;
+public ICODecoder(byte[] decodand, int offset, int len) {
+this.decodand = decodand;
+this.offset = offset;
+this.len = len;
+}
+/**
+* Decode the Icon Directory for this ICO and store the result in iconDirectory.
+*
+* @return true if ICO decoding was considered to probably be a success, false if it certainly
+*         was a failure.
+*/
+private boolean decodeIconDirectoryAndPossiblyPrune() {
+hasDecoded = true;
+// Fail if the end of the described range is out of bounds.
+if (offset + len > decodand.length) {
+return false;
+}
+// Fail if we don't have enough space for the header.
+if (len < ICO_HEADER_LENGTH_BYTES) {
+return false;
+}
+// Check that the reserved fields in the header are indeed zero, and that the type field
+// specifies ICO. If not, we've probably been given something that isn't really an ICO.
+if (decodand[offset] != 0 ||
+decodand[offset + 1] != 0 ||
+decodand[offset + 2] != 1 ||
+decodand[offset + 3] != 0) {
+return false;
+}
+// Here, and in many other places, byte values are ANDed with 0xFF. This is because Java
+// bytes are signed - to obtain a numerical value of a longer type which holds the unsigned
+// interpretation of the byte of interest, we do this.
+int numEncodedImages = (decodand[offset + 4] & 0xFF) |
+(decodand[offset + 5] & 0xFF) << 8;
+// Fail if there are no images or the field is corrupt.
+if (numEncodedImages <= 0) {
+return false;
+}
+final int headerAndDirectorySize = ICO_HEADER_LENGTH_BYTES + (numEncodedImages * ICO_ICONDIRENTRY_LENGTH_BYTES);
+// Fail if there is not enough space in the buffer for the stated number of icondir entries,
+// let alone the data.
+if (len < headerAndDirectorySize) {
+return false;
+}
+// Put the pointer on the first byte of the first Icon Directory Entry.
+int bufferIndex = offset + ICO_HEADER_LENGTH_BYTES;
+// We now iterate over the Icon Directory, decoding each entry as we go. We also need to
+// discard all entries except one >= the maximum interesting size.
+// Size of the smallest image larger than the limit encountered.
+int minimumMaximum = Integer.MAX_VALUE;
+// Used to track the best entry for each size. The entries we want to keep.
+SparseArray<IconDirectoryEntry> preferenceArray = new SparseArray<IconDirectoryEntry>();
+for (int i = 0; i < numEncodedImages; i++, bufferIndex += ICO_ICONDIRENTRY_LENGTH_BYTES) {
+// Decode the Icon Directory Entry at this offset.
+IconDirectoryEntry newEntry = IconDirectoryEntry.createFromBuffer(decodand, offset, len, bufferIndex);
+newEntry.index = i;
+if (newEntry.isErroneous) {
+continue;
+}
+if (newEntry.width > Favicons.largestFaviconSize) {
+// If we already have a smaller image larger than the maximum size of interest, we
+// don't care about the new one which is larger than the smallest image larger than
+// the maximum size.
+if (newEntry.width >= minimumMaximum) {
+continue;
+}
+// Remove the previous minimum-maximum.
+preferenceArray.delete(minimumMaximum);
+minimumMaximum = newEntry.width;
+}
+IconDirectoryEntry oldEntry = preferenceArray.get(newEntry.width);
+if (oldEntry == null) {
+preferenceArray.put(newEntry.width, newEntry);
+continue;
+}
+if (oldEntry.compareTo(newEntry) < 0) {
+preferenceArray.put(newEntry.width, newEntry);
+}
+}
+final int count = preferenceArray.size();
+// Abort if no entries are desired (Perhaps all are corrupt?)
+if (count == 0) {
+return false;
+}
+// Allocate space for the icon directory entries in the decoded directory.
+iconDirectory = new IconDirectoryEntry[count];
+// The size of the data in the buffer that we find useful.
+int retainedSpace = ICO_HEADER_LENGTH_BYTES;
+for (int i = 0; i < count; i++) {
+IconDirectoryEntry e = preferenceArray.valueAt(i);
+retainedSpace += ICO_ICONDIRENTRY_LENGTH_BYTES + e.payloadSize;
+iconDirectory[i] = e;
+}
+isValid = true;
+// Set the number of images field in the buffer to reflect the number of retained entries.
+decodand[offset + 4] = (byte) iconDirectory.length;
+decodand[offset + 5] = (byte) (iconDirectory.length >>> 8);
+if ((len - retainedSpace) > COMPACT_THRESHOLD) {
+compactingCopy(retainedSpace);
+}
+return true;
+}
+/**
+* Copy the buffer into a new array of exactly the required size, omitting any unwanted data.
+*/
+private void compactingCopy(int spaceRetained) {
+byte[] buf = new byte[spaceRetained];
+// Copy the header.
+System.arraycopy(decodand, offset, buf, 0, ICO_HEADER_LENGTH_BYTES);
+int headerPtr = ICO_HEADER_LENGTH_BYTES;
+int payloadPtr = ICO_HEADER_LENGTH_BYTES + (iconDirectory.length * ICO_ICONDIRENTRY_LENGTH_BYTES);
+int ind = 0;
+for (IconDirectoryEntry entry : iconDirectory) {
+// Copy this entry.
+System.arraycopy(decodand, offset + entry.getOffset(), buf, headerPtr, ICO_ICONDIRENTRY_LENGTH_BYTES);
+// Copy its payload.
+System.arraycopy(decodand, offset + entry.payloadOffset, buf, payloadPtr, entry.payloadSize);
+// Update the offset field.
+buf[headerPtr + 12] = (byte) payloadPtr;
+buf[headerPtr + 13] = (byte) (payloadPtr >>> 8);
+buf[headerPtr + 14] = (byte) (payloadPtr >>> 16);
+buf[headerPtr + 15] = (byte) (payloadPtr >>> 24);
+entry.payloadOffset = payloadPtr;
+entry.index = ind;
+payloadPtr += entry.payloadSize;
+headerPtr += ICO_ICONDIRENTRY_LENGTH_BYTES;
+ind++;
+}
+decodand = buf;
+offset = 0;
+len = spaceRetained;
+}
+/**
+* Decode and return the bitmap represented by the given index in the Icon Directory, if valid.
+*
+* @param index The index into the Icon Directory of the image of interest.
+* @return The decoded Bitmap object for this image, or null if the entry is invalid or decoding
+*         fails.
+*/
+public Bitmap decodeBitmapAtIndex(int index) {
+final IconDirectoryEntry iconDirEntry = iconDirectory[index];
+if (iconDirEntry.payloadIsPNG) {
+// PNG payload. Simply extract it and decode it.
+return BitmapUtils.decodeByteArray(decodand, offset + iconDirEntry.payloadOffset, iconDirEntry.payloadSize);
+}
+// The payload is a BMP, so we need to do some magic to get the decoder to do what we want.
+// We construct an ICO containing just the image we want, and let Android do the rest.
+byte[] decodeTarget = new byte[ICO_HEADER_LENGTH_BYTES + ICO_ICONDIRENTRY_LENGTH_BYTES + iconDirEntry.payloadSize];
+// Set the type field in the ICO header.
+decodeTarget[2] = 1;
+// Set the num-images field in the header to 1.
+decodeTarget[4] = 1;
+// Copy the ICONDIRENTRY we need into the new buffer.
+System.arraycopy(decodand, offset + iconDirEntry.getOffset(), decodeTarget, ICO_HEADER_LENGTH_BYTES, ICO_ICONDIRENTRY_LENGTH_BYTES);
+// Copy the payload into the new buffer.
+final int singlePayloadOffset =  ICO_HEADER_LENGTH_BYTES + ICO_ICONDIRENTRY_LENGTH_BYTES;
+System.arraycopy(decodand, offset + iconDirEntry.payloadOffset, decodeTarget, singlePayloadOffset, iconDirEntry.payloadSize);
+// Update the offset field of the ICONDIRENTRY to make the new ICO valid.
+decodeTarget[ICO_HEADER_LENGTH_BYTES + 12] = (byte) singlePayloadOffset;
+decodeTarget[ICO_HEADER_LENGTH_BYTES + 13] = (byte) (singlePayloadOffset >>> 8);
+decodeTarget[ICO_HEADER_LENGTH_BYTES + 14] = (byte) (singlePayloadOffset >>> 16);
+decodeTarget[ICO_HEADER_LENGTH_BYTES + 15] = (byte) (singlePayloadOffset >>> 24);
+// Decode the newly-constructed singleton-ICO.
+return BitmapUtils.decodeByteArray(decodeTarget);
+}
+/**
+* Fetch an iterator over the images in this ICO, or null if this ICO seems to be invalid.
+*
+* @return An iterator over the Bitmaps stored in this ICO, or null if decoding fails.
+*/
+@Override
+public ICOIterator iterator() {
+// If a previous call to decode concluded this ICO is invalid, abort.
+if (hasDecoded && !isValid) {
+return null;
+}
+// If we've not been decoded before, but now fail to make any sense of the ICO, abort.
+if (!hasDecoded) {
+if (!decodeIconDirectoryAndPossiblyPrune()) {
+return null;
+}
+}
+// If decoding was a success, return an iterator over the images in this ICO.
+return new ICOIterator();
+}
+/**
+* Decode this ICO and return the result as a LoadFaviconResult.
+* @return A LoadFaviconResult representing the decoded ICO.
+*/
+public LoadFaviconResult decode() {
+// The call to iterator returns null if decoding fails.
+Iterator<Bitmap> bitmaps = iterator();
+if (bitmaps == null) {
+return null;
+}
+LoadFaviconResult result = new LoadFaviconResult();
+result.bitmapsDecoded = bitmaps;
+result.faviconBytes = decodand;
+result.offset = offset;
+result.length = len;
+result.isICO = true;
+return result;
+}
+/**
+* Inner class to iterate over the elements in the ICO represented by the enclosing instance.
+*/
+private class ICOIterator implements Iterator<Bitmap> {
+private int mIndex = 0;
+@Override
+public boolean hasNext() {
+return mIndex < iconDirectory.length;
+}
+@Override
+public Bitmap next() {
+if (mIndex > iconDirectory.length) {
+throw new NoSuchElementException("No more elements in this ICO.");
+}
+return decodeBitmapAtIndex(mIndex++);
+}
+@Override
+public void remove() {
+if (iconDirectory[mIndex] == null) {
+throw new IllegalStateException("Remove already called for element " + mIndex);
+}
+iconDirectory[mIndex] = null;
+}
+}
+}

The Tor Browser / file comparison

comparison: mobile/android/base/favicons/decoders/ICODecoder.java

mobile/android/base/favicons/decoders/ICODecoder.java